Tuning arrangement for radio communication



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. C. SCHWARZ TUNING ARRANGEMENT FOR RADIO COMMUNICATION Filed Oct. 31. 1.921

11 600m ,y; ,1 :4 0, 500m Patented Nov. 15, 1927.

UNITED STATES PATENT; oFFIc CARL SCHWARZ, OF CHARLOTTENBURG, NEAR BERLIN GERMANY, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 01 PENNSYLVAN T'IINING ARRANGEMENT FOB RADIO COMMUNICATION.

Application filed October 31, 1921, Serial No; 511,825, and in Germany April 12,1921.

This invention relates to radio system for communication with a number of stations.

It is an object of this invention to provide for a quick adjustment at an station to 5 enable it to send and receive. om any selected one of the other stations.

It is a further, object of this invention to provide a selection of wave lengths for sending' and receiving which will enable any station of the system to readily communicate with any other stationwithout disturbmg any except the desired station.

It isa further object of this invention to provide a switching device which shall change the tuning so as to adapt the apparatus for communication with the selected the actuation of a single switch FIgure 1, 1s a diagrammatic represents} tion of the assignment of wave lengths to the several stations of the'system.

Figure 21s a diagram of the switchm apparatus and the connections associate therewith in the sending device at any one station. a

Figure 3 is a similar diagram for the receiving apparatus. In the system employing this invention a wave length is assigned to each station, to which its receiving apparatus is normally tuned, so that radiations sent out on this wave length will always actuate the receiving apparatus in this station when such apparatus is normally tuned. Each 8133121701118 ac tions of a plurality of wave lengts, corresponding to the wave lengths WhlCh the other stations are normall tuned to recelve.

Thus, in Figure 1, t ree stations are A shown, at A, B and C. The station at A has I 4 for 500 m. and the station at C for 600 m.

are against the contacts 1. In the opposite also provided with means for sending radia- The station at A has sending apparatus which may be adjusted for sendin radiations of 500 m. wave length when t e operator wishes to communicate with station B. The apparatus at station A is also capable of being adjusted for sending radiations of 600 m. wave length when the operator there wishes to communicate with station 0.

Similarly the apparatus at station B can 'radiateat 400 m. or 600 m. and the apparatus at station C at either 400 m. or 500 m. From this description it will be obvious how the system can be ada ted to any number of stations insteadof t ree. At T, in Fig.- ure 1, is represented a traveling station which should be equipped with apparatus for receiving or sending any of t e wave lengths mentioned. The connections betweenA, B and G, are intended to represent the wires of a high tension ower line and this system is particularly a apted for radio communication over such wlres. It is, however, obvious that the system ofassigning wave lengths just described is equally applicable to any form of radio communicatlon, with or without wires.-

In Fig. 2, the sending apparatus is illustrated as having two antennae A and A, each of which is grounded at E by a common connection. The antenna A is connected through a secondary '5 to the ground connection. This connection is'controlled by a switch having three blades. The mechanical connection between these 'blades is indicate by the dot and dash linefi. In the illustrated position of the switch the blades position the blades are againstathe contacts 2. With the switch in the illustrated position, the whole of the inductor 5 is included between the antenna and the ground. In the opposite position only a part of this inductor is thus included and the variable inductance 7 is substituted for the part of the inductor 5 switched out.

A similar arrangement in the connection of the antenna A to the ground is shown, but there the variable inductancefiand the whole of the inductor 9 are included in the connection when the switch is in the illustrated position. With the switch in the opposite position, onl a portion ofgthe inductor 9 is included in this connection,

the remainder of the inductor and the variable inductance both being excluded. The ammeter 11 is included in the connection between the antenna A and the ground in both positions of the switch.

With the switch in the illustrated position, the radiating system, including the antennae A and A, the whole of the inductor 5, the variable inductance 8 and the whole of the inductor 9, is connected to ground at approximately its central point. This point would be a potential node if the adjustment were exact. Consequently the connection to ground ensures the desired distribution of potential, even when the adjustment is inexact. In this position of the switch, the maximum inductance is included in a radiating circuit, consequently the circuit is adjusted for long wave lengths.

The oscillating circuit, which is only partly illustrated because the remainder of it presents no peculiar features, includes the primary coils 12 and 13, the whole of each,

coil being included in the circuit in the illustrated position of the switch. In the opposite position of the switch, a portion only of each coil is thus inc'luded. When the switch, therefore, is in the position for the radiating circuit to give a long wave length, the oscillating circuit also is adjusted for this long wave length. Proper tuning between the two circuits is thus maintained. When the switch is in the opposite position, connecting the contacts 2, the radiating circuit contains less inductance and is, therefore, adjusted for a shorter wave length and a simultaneous change of the same nature is made in the oscillating circuit.

The tuning of the radiation circuit, in the illustrated position of the switch, can be ale tered slightly by means of the variable inductance 8. Slight changes in the character of the circuit can thus be corrected. With the switch in this position, a change of the adjustment of the variable inductance 7 will be without effect because this variometer is disconnected at the switch. Manipulation of the variometer 7 will, therefore, produce no effect either in the length of the wave radiated or in the reading of the ammeter 11. It is, however, desirable that the adjustment of this variometer be left unchanged in order that, when the switch is moved to the opposite position, the adjustment for the shorter wave length shall be at once accomplished. If desired, this may be ensured by providing such an interlocking arrangement that the adjustment of the variometer 7 cannot be altered except when the switch is in the position opposite that illustrated. This interlocking arrangement would also provide for locking the variometer 8 except when the switch is in the illustrated position. Thus neither variometer can be changed. except when the apparatus is sending upon the wave length controlled by that variometer. Inadvertent throwing out of tune is thus avoided.

Although, in the normal use of the system illustrated in Figure 1, no change is made in the receiving apparatus, provision is made for such a change, in order that the operator may depart from the illustrated assignment of wave lengths when desired, He might do this, for example, to listen to the message intended for some other station. Thus, if the operator at station A were sending on a wave length of 600 m., in order that station 0 should receive the message, the operator at station B by changing his receiving apparatus from 500 m. to 600 m. would hear the message intended for station G. The operator at station A, for example, might direct the operators at all the other stations to each put his receiving apparatus upon the wave length assigned to station C so that the operator at station A could deliver a message simultaneously to all of the stations.

The means for accomplishing this are illustrated in Figure 3, where 14 and 15 are receiving antennae. These are connected through the primary coil 16, to which the secondary coil 17 can be adjustably coupled. A condenser 18 is permanently connected in parallel with the coil 16 and a condenser 19 is similarly related to the coil 17. The tuning of the receiving apparatus is changed by switching supplemental condensers into circuit in parallel with the condensers l8 and 19. The switch 21 when in the illustrated position connects a condenser 22 in parallel with the condenser 18 and a condenser 23 in parallel with the condenser 19. The condensers 22 and 23 are of the proper capacity to make the tuning of the receiving circuit correct for the longer wave lengths. When the switch 21 is in the opposite position, the condenser 24 is connected in parallel with the condenser 19. The condensers 24 and 25 are of the proper capacity to tune the receiving circuit for the shorter wave lengths. All four condensers 22 to 25 are made adjustable to provide for slight changes in the constants of the circuits. If desired, an interlocking arrangement may be provided, so that the adjustment of any of these condensers cannot be changed when that condenser is out of circuit.

To those skilled in the art, many variations of the details of the apparatus will at once be obvious and the fact that but one embodiment of the invention is illustrated is not to be taken as indicating any intention of limiting the invention.

I claim as my invention:

1. In a radio device, an antenna circuit, a

reactance permanently connected in said circuit, an adjustable reactance, a switching device which when in one position places said adjustable reactance in the antenna circuit and when in the opposite position removes said adqustable reactance from the antenna circuit, and lnterlockmg meanspreventing change of said adjustable rea'ctance except whenit is in circuit.

2. In a radio sending apparatus, a pair of antennae, a fixed inductor connected to each antenna, a variometer connected to each fixed inductor, and a switching device for alternately removing said variometers from the circuit. J

3, In a radio sending apparatus, a pair of antennae, a fixed inductor connected to each antenna, a variometer connected to each fixed inductor, a switching device for alter- 15 nately r'emovin said variometers from the circuit, and an lnterlocking device controlled by said switching device and preventing adjustment of the variometer not in circuit.

In testimony whereof I aflix my signature. 

